OCR GCSE PHYSICS P7 OCR physics Unit 3 1.5 / 5 PhysicsAstronomyGCSE Created by: Mohammed ZubairCreated on: 28-05-12 09:29 P7A A SOLAR DAY is 24hrs A SIDEREAL DAY is 24hrs and 56mins a solar day is 4 minutes longer than a sidereal THE MOON TAKES 24hrs and 49mins to appear in the same part of the sky. IT TAKES 28 DAYS TO COMPLETE ONE ORBIT!!! 1 of 3 ECLIPSES A SOLAR ECLIPSE IS WHEN THE MOON LINES UP EXACTLY WITH THESUN AND THE EARTH AND BLOCK SUNLIGHT FROM REACHING THE EARTH. A LUNAR ECLIPSE IS WHEN THE EARTH'S SHADOW STOPS THE SUNLIGHT FROM REACHING THE EARTH(THE MOON APPEARS RED) 2 of 3 CALCULATIONS POWER(dioptres) =1 / focal length(metres) MAGNIFICATION = FO/FE 1 ARCSECOND= 1/3600 DISTANCE(pc) = 1/ angle in arcseconds SPEED OF RECESSION(kms) =HUBBLE CONSTANT (s)*DISTANCE(km) 3 of 3
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